Diesel exhaust particle exposure causes redistribution of endothelial tube VE-cadherin

Abstract

Whether diesel exhaust particles (DEPs) potentially have a direct effect on capillary endothelia was examined by following the adherens junction component, vascular endothelial cell cadherin (VE-cadherin). This molecule is incorporated into endothelial adherens junctions at the cell surface, where it forms homodimeric associations with adjacent cells and contributes to the barrier function of the vasculature Venkiteswaran et al., 2002;Villasante et al., 2007). Human umbilical vein endothelial cells (HUVECs) that were pre-formed into capillary-like tube networks in vitro were exposed to DEPs for 24 hr. After exposure, the integrity of VEcadherin in adherens junctions was assessed by immunofluorescence analysis, and demonstrated that increasing concentrations of DEPs caused increasing redistribution of VE-cadherin away from the cell-cell junctions toward intracellular locations. Since HUVEC tube networks are threedimensional structures, whether particles entered the endothelial cells or tubular lumens was also examined. The data indicate that translocation of the particles does occur. The results, obtained in a setting that removes the confounding effects of inflammatory cells or blood components, suggest that if DEPs encounter alveolar capillaries in vivo, they may be able to directly affect the endothelial cell-cell junctions.

Diesel exhaust particulate extracts inhibit transcription of nuclear respiratory factor-1 and cell viability in human umbilical vein endothelial cells

“…Here we demonstrated that DEPEs inhibit the basal transcription of NRF-1. Although the levels of DEPEs used in these experiments are likely higher than actual inhaled levels of DEPs, the i n vivo concentrations of inhaled DEP reaching endothelial surfaces cannot be measured and an estimate would require detailed knowledge of inhalation capacity, rates and sites of DEP deposition, PM size distribution, measurements of clearance, and transmigration of the particles through the alveolar membranes to the capillary endothelial cells (Chao et al 2011). The concentrations of DEPEs examined here is comparable (Chao et al 2011) or less than ((Li et al 2010b) used 25–50 μg/ml DEPE) those used in other in vitro studies demonstrating the impact of DEPEs on endothelial function.…”

“…Evidence linking inhaled DEPs to adverse health effects including cardiovascular disease has been reviewed (Monforton 2006). Although the mechanism by which DEPs gain access to the circulation is unclear, a small percentage of inhaled PMs have been found in circulation (Chao et al 2011). …”

DEP induction of ROS in capillary-like endothelial tubes leads to VEGF-A expression

“…Human umbilical vein endothelial cells (HUVECs) were cultured in endothelial cell growth medium EBM-2 Bulletkit (Lonza) as previously described (Chao et al, 2011). Medium was supplemented with phosphate buffered saline and Tween-80 to make a final concentration of 1X PBS, 0.05% Tween-80.…”

“…By particle number, about 14% of these DEPs were between 20 and 100 nm (i.e., PM 0.1 ) and about 85% were less than 2.5 µm. The results of our previously reported in vitro endothelial tube culture experiments demonstrated that the adherens junction component, VE-cadherin, moved from cell-cell junctions to intracellular locations after exposure (Chao et al, 2011). Such rearrangement of cell-cell junctions is associated with permeability (for review see Dejana et al, 2008), and VE-cadherin is an important player in this property.…”

“…Using in vitro capillary tubes as a simplified vascular model system for this process, it was previously shown that DEPs induce the redistribution of vascular endothelial cell-cadherin (VE-Cad) away from the plasma membrane to intracellular locations. This allowed DEPs into the cell cytoplasm and tube lumen, suggesting the tubes may have become permeable (Chao et al, 2011). Here some of the mechanisms responsible for endothelial tube changes after DEP exposure were examined.…”